The effects of hemorrhagic shock on the hearts of dogs and other animals will be studied. Characteristic lesions have been previously described in the subendocardial region which may in part be related to the increased catecholamine output in shock. The present studies will attempt to determine the effects of reserpine treatment on myocardial lesion formation in shock, as well as the effects of treatment of shock by exogenous 1-norepinephrine given intravenously. In addition, electron microscopic observations of the early and late sequential changes in zonal lesion formation will be carried out. Studies will also be done of the effects of alpha-adrenergic blockade on phasic coronary blood flow in hemorrhagic shock.